Chemical anchoring adhesives are known which are composed of two or more components that react together and cure when mixed. U.S. Pat. No. 5,730,557, issued to Skupian et al., discloses a mortar mixture capsule unit for chemical attachment of anchors in boreholes. The capsule houses a filler material, and a chemical binder system contained in smaller capsules within the filler material. The cartridge is inserted into a borehole, and a driving tool is used to insert an anchor. The driving tool imparts motion to the anchor, which ruptures both the housing capsule and the smaller capsules contained within it, causing the chemical binder system to interact and mix with the filler. The interaction and mixing causes reaction and curing of the binder system/filler mixture, thereby securing the anchor within the borehole. A similar adhesive is sold by Hilti AG under the trade name "HVU".
U.S. Pat. No. 5,731,366, issued to Moench et al., discloses a chemical plugging compound based on a free-radically polymerizable resin and a free-radical initiator spatially separated from the resin. The spatial separation can be effected by encapsulating the initiator in glass, gelatin or cellulose capsules. The plugging compound is described as being self-supporting and storage stable.
This and other prior art chemical anchoring adhesives have certain disadvantages. One disadvantage is that one or both components are fluid, and must be wrapped, encapsulated or otherwise enclosed in a package prior to use. Thus, it is not easy to vary the amount of adhesive used in a borehole, or the size of the housing capsule, while at the job site. Put another way, oversized and undersized boreholes will receive the same amount of predetermined, pre-packaged adhesive as boreholes of standard size.
Another disadvantage is that the fluid adhesives may flow or spill from the boreholes during use, particularly after the package is ruptured by the anchor being driven. This problem is especially acute when the borehole is upside down and vertical, but also exists when the borehole is horizontal, or at an angle between horizontal and upside down vertical. Even when the adhesive is not completely fluid, the prior art cartridges are typically not self-retentive, i.e., the cartridges will fall from overhead boreholes.
Another disadvantage is that the two components, binder and filler, must be completely segregated prior to use, to prevent premature interaction and reaction. The encapsulation techniques used to accomplish this require some precision and expense. Also, there is no assurance that the smaller capsules used to contain the binder will remain evenly dispersed among the filler until the adhesive capsule is used. Uneven dispersion of the binder and filler can lead to uneven or inadequate adhesion of the anchor.
Cartridge adhesives are another type of prior art adhesive. Cartridge adhesives include two separate parts which are simultaneously injected into a borehole using a two-barrel caulking gun which brings the two parts together at the point of injection, whereupon they react upon entering the borehole. Disadvantages of cartridge adhesives include excessive packaging waste, excessive adhesive waste due to unmixed, unused material remaining in the caulking barrels, and insufficient viscosity, which permits the material to run out of vertical overhead boreholes, and to sag in horizontal boreholes.